This invention relates generally to dishwashing machines, and more particularly to soil collectors for dishwashing machines of the domestic or household type.
Dishwashers of this type generally consist of an enclosed cabinet having a bottom hinged door at the front closing off an otherwise sealed tube having a sump formed at the bottom portion thereof. The dishes are generally placed on upper and lower racks which are arranged to slide or roll in and out of the dishwasher when the door is open for loading and unloading the articles to be washed. Generally, these racks are arranged so that plates, pots and pans and other large articles are placed on the lower rack while smaller articles like cups and glasses are placed on the upper rack which is located close to the top of the compartment. The dishwashers all generally have a rotating lower wash arm which rotates as a reaction to jets of liquid and carries a number of spray openings directing the water upward as the arm rotates to spray all of the dishes in the interior. Certain of the machines also have the second level wash arm located above the lower rack and below the upper rack to provide additional washing ability. Furthermore, many dishwashers also have a third level wash arm located centrally beneath the top wall of the cabinet to spray fluid down on all of the dishes in both the upper and lower racks.
The dishwashing cycle consists of alternate cycles of washing and rinsing in which the washing cycle is distinguished generally only by the length of time and the fact that a detergent has been added to the wash water. During the cycle, the water is drawn from the sump at the bottom and passes through a pump to the wash arms from which, after passing over the dishes in the racks, it returns to the bottom sump. Between the cycles, it is necessary to provide a drain for the fluid within the machine so that it can receive a refill of fresh water.
Generally, the pumping action of dishwashers falls into two categories. In one of these, there are separate pumps for wash circulation and drain which may be driven by the same motor, and in which the pumps are arranged so that each pump is effective only in one direction of rotation of the motor. Thus, when it is desired to recirculate wash water, the pump rotates in one direction, and when it is desired to drain the water from the interior, the motor rotates in the opposite direction to actuate the drain pump. The other type of machine uses a single pump with a unidirectional, non-reversible motor. Thus, at all times the water is drawn from the inlet at the bottom of the sump and passes through the pump to an outlet area. In this area is a diverter valve, which may be solenoid-actuated, and which serves to direct fluid either to the wash arms and the interior of the tub or to drain. By having the drain outlet closer to the pump impeller, the diverter valve is operable in one position to close off the drain line and direct all of the fluid further downstream, where it may pass through separate conduits to second and third level wash arms, while the major portion of the flow goes to the lower wash arm. When the diverter valve is actuated by a solenoid, the valve swings to close off the downstream portion so that all of the fluid passes out the drain line. With such an arrangement, the pressure of the flow against the valve would hold it in the closed position even if the solenoid is de-energized, so that the valve could not return to the wash position until all of the fluid had effectively been drained from the machine. Such an arrangement may be found in U.S. Pat. No. 3,367,368, granted Feb. 6, 1968.
A problem encountered by dishwashers of all types is that of handling the soil removed from the dishes and other items being washed in the dishwasher. Such soil, as it is washed off the dishes, passes into the water in the sump, and thus is drawn into the pump inlet and recirculated through the wash arms during a wash or rinse cycle, and is therefore subject to being redeposited on the dishes from which it had originally been removed. If the soil particles are particularly large, they will be blocked by an inlet screen in the sump from passing into the pump, and can be removed manually after the washing cycle has been completed. However, removal of soil of this type is only a small portion of the problem, since the screen must be relatively coarse so as not to become clogged by excessive particles and the likelihood that the screen will not be cleaned by hand after every wash cycle. Thus, it must be expected that most of the soil removed from the dishes will necessarily tend to be recirculated through the pump and wash arms and subject to possible redeposit on the dishes being washed.
In the case of dishwashers having separate drain and recirculation pumps, the solution to this problem has been to provide a form of collector or filter arranged in such a manner that when the machine is in a recirculating cycle such as washing or rinsing, the fluid, or at least part of it, will pass through a screen or filter, and thereby be removed from the recirculating cycle. Such a filter or screen must necessarily be cleaned often, and various arrangements have been proposed whereby the screen is automatically cleaned by water going to the drain from the drain pump during the drain cycle so that the soil particles caught on the screen or filter pass directly to drain and the screen or filter is cleaned for the next portion of the wash cycle.
Such an arrangement has heretofore not been possible in dishwashers using a single unidirectional pump. Therefore, machines of this type generally are provided with a macerator or cutting blade at the pump inlet which may be attached to the pump impeller so as to cut or break up soil particles as they are continuously recirculated through the pump until they become sufficiently fine as to become suspended in the recirculating fluid and less likely to be redeposited on the dishes. Thus, by using a succession of several wash cycles with interposed rinse cycles, soil will be eventually discharged to drain under the drain cycle so that the final rinse cycle will consist of essentially pure water with a minimum of soil particles.